Process for treating oils



Oct. 22, 1940. .1. A. CAMPBELL, JR

PRUCESS FOR TRETIINGl OILS Filed Sept. 25, 1954 Patented Oct. 22, 1940 UNITED STATES PATENT oFFicE PROCESS Fon TREATING oILs Application September 25, 1934, Serial No. 745,416

` i 6 claims. (ci. 19e-1s) The present invention relatestd an improved process for separatingasphalt and/0r wax from petroleum oils. The invention relates particularly to a process for producing lubricating oil by separating impurities such as asphalt and/or wax from oils containing the same.

It has been discovered that when a waxy oil is comrningled with a solvent or diluent at a reduced temperature, say 0 F. to-40 F., the waxy oil becomes crystallized or vsolidiiies to form a congealed mass of oil and wax. Upon continued contact of the solidified oil and wax such as takes place when the solidified particles settle gradually to the bottom of the container of ychilled solvent, solution of theoil in the resulting solvent takes place `corresponding to a leaching out of the oil fractions from the wax matrix leaving the wax particles undissolved. This process distinguishes from former practice in that instead oi the wax and oil being first dissolved in the diluent and the wax subsequently crystallized out of solution, the waxy oil is first solidified and solution of the oil takes place so` that the oil is leached from the wax without dissolving any material portion of the wax. The wax, forthe most part, is obtained in a large or coarse flake-like form which readily settles out or ltersand hence reduces the mechanical difculties normally encountered from iine dispersion of wax. A small amount of the crystallized wax may remain in suspension but this can be easily removed by filtration.

The rate of waxy oil introduction into the cold solvent is extremely important since if the rate is too rapid, the sprayed solidiiied oil and wax will tend to ball up or agglomerate into large masses from which the oil is leached with great diliiculty. The rate oi waxy oil introduction into the cold leaching solvent will depend largely upon the temperature oi the waxy oil when introduced into the leaching solvent or in other words, ,the

rate will depend upon the viscosity of the waxy oil at the temperature of introduction into the solvent. As will be pointed out, oils having low viscosities at the temperature of introduction into the cold leaching solvent crystallize as spongy masses which agglomerate readily at the top of the leaching column. This spongy mass descends or settles rather slowly through the leaching solvent. Such oils must necessarily be introduced rather slowly in order to permit proper leachingA the leaching solvent crystallize as Strings or pel-V lets which descend rapidly through the solvent. These oils may be introduced at a greater rate than the oils of low viscosity provided the height of the column is suilicient to provide adequate leaching of the occluded oil from the crystallized wax.

The rate of oil introduction cannot be given in exact gures since this will depend upon the size or height of the leaching column, the ratio of solvent to waxy oil and the character of leaching solvent and waxy oil. However, the rate may be readily determined by anyone `skilled in the art. When using liquid propane at a temperature of 40 F. as the leaching solvent in a ratio of approximately` 5 volumes of the propane to one of the waxy oil, I have found that it requires approximately one hour for the solvent to thoroughly leach out the occluded oil from the wax matrices. Therefore, if the propane is introduced countercurrent to the waxy oil at a rate of 200 barrels per hour, the oil should be sprayed into the top of the leaching column at a rate of not in excess oi forty barrels per hour in order to provide a leaching time of one hour. In the particular case, the oil sprayed had a viscosity of less than 500 seconds Saybolt Universal at F. and the waxy oil solidified in iiaky form when sprayed into the cold solvent. It is obvious. that if the oil had been solidied, bythe leaching solvent as strings or pellets, the leaching time would be greater. Also, if the propane to oil ratio were increased, the leaching time would be decreased. Propane has a high solvent power for oil at low temperatures; obviously, therefore, by using other solvents not having as great a solvent power for oil at low temperatures as propane, `the leaching time and/or solvent to oil ratio 'would necessarily be increased to give properwashing of the crystallized wax. y

As indicated above, the occluded oil in the crystallized particles is gradually leached from the structure as the particles settle to the bottom of the leaching column. The wax structure remains Y practically in the shape as when the waxy oil is first crystallized at the top oi the column. However, due to the fact that the cementing oil is removed, the crystallized wax particles are extremely fragile and will break into finely divided particles if the same are subjected to severe agitating conditions. Such iinely divided wax particles are diiiicult to separate from the oil by such means as settling or iiltering. l

It is thus important to prevent substantial working of the solidified particles at the top of the leaching lcolumn so as to prevent agglomerai low viscosity directly tion and at the bottom after the oil has been leached out of the crystallized structure so as to prevent rupture of the crystallized wax particles.

Preferably the oil is introduced. into the cold solvent in such manner that leaching of the oil by the solvent takes place rapidly. If the oil is introduced into the cold solvent as a spray or ne streams, solidiiication takes place upon the surface of the cold solvent as iiat buttons or flakes. The solvent may then readily dissolve out the oil from the solidiiied particles leaving wax matrices which have been thoroughly washed from oil and which settle rapidly to the bottom of the decanter in which the leaching operation takes place. The size of the solidified waxy oil particles will, of course, depend upon the leaching conditions desired, that is, the time desired to complete the leaching operation, which will in turn depend upon the character of the waxy oil and the solvent to oil ratio during leaching. Preferably, however, the size of the solidiiicd oil paiticles should not be too thick, since the leaching time increases considerably. I have found that sufficiently rapid leaching will be obtained when the waxy oil is solidied in thicknesses substantially not greater than 1A; in. at its smallest dimension. I may solidify the waxy oil as flat buttons or akes or pellets l@ in. thick or as. long strings M1 in. in diameter or even as sheets 1/4. in. thick.

While I may operate by spraying the oil at a into the reirigerating diluent, I preferably operate in such manner as to first obtain good crystallization of the wax in the oil and follow this by leaching out the occluded oil. I may accomplish this by chilling the oil, for example, to below its pour point in the absence of a diluent and subsequently spray or 40, otherwise introduce the crystallized wax and oil into the cold leaching diluent. If desired, the waxy oil may be subjected to a digesting operation at a low temperature preferably at a temperature below the pour point of the waxy oil so as to permit good crystallization of the wax in the oil and subsequently leach out the occluded oil. The leaching temperatiue or temperature of the leaching solvent may then be either at the temperature of digestion or slightly below. By operating in this manner substantially little or no wax will be dissolved in the leaching diluent and thus less diiliculty will be encountered with subsequent recrystallization of wax in finely dispersed form and effects of solvation of oil in the wax.

Another method for preparing the waxy oil prior to leaching resides in chilling the waxy oil to below its pour point, then working the waxy oil to break up the gel and form a iiuid mass and repeating this operation of chilling and breaking up the gel until substantially all of the wax has been crystallized into good wax crystals. This mixture may then be sprayed or introduced as small particles into the cold leaching solvent. It will be observed that when the waxy oil is chilled to below its pour point, a portion of the wax crystallizes out of the oil and the mass becomes a gel. This gel may be made readily fluid again by working such as by gently stirring the rnass. However, when the gel is broken, the crystallized wax will not redissolve in the oil. By repeating this operation of chilling to say a lower temperature, the mass will again become a gel forming new wax crystals which may again be broken or rendered fluid by further working. After a number of such operations of chilling and breaking the gel, the wax present in the oil may be substantially all crystallized into large Wax crystals. This mixture may then be sprayed or otherwise introduced into the cold leaching solvent.

It has been observed that the character of the waxy oil regarding its viscosity at the temperature of introduction into the cold leaching solvent and also the character of the leaching solvent itself influences the character of crystallization in the solvent. However, when employing normally liquid or substantially non-volatile solvents such as casinghead gasoline, hexane, pentane and the like, an oil of any viscosity whether high or low, will crystallize in the cold leaching solvent in the form of strings or pellets. On the other hand, when waxy oils are sprayed into highly volatile or liqueed normally gaseous hydrocarbon solvents, for example propane, the viscosity of the waxy oil at the temperature of introduction will determine whether the waxy oil will crystallize'as strings or pellets or as a spongy mass. If the viscosity of the oil is low7 for ex ample, below 500 seconds Saybolt Universal at the temperature of spraying into the cold leaching solvent, crystallization takes place as a spongy mass. This is perhaps due to the fact that as the sprayed particles contact the cold leaching solvents, the sprayed particles solidify as bubbles containing volatile leaching solvent which burst dueto the vaporization of the solvent forming a solidied foam-like substance. When oils of high viscosity, for example, approximately 50G seconds Saybolt Universal or higher at the temperature of introduction, are sprayed into such volatile solvents, crystallization takes place as strings or pellets. The viscosity of the oil can be low, either due to its intrinsic nature or because of predilution with a diluent or because of its being heated to an elevated temperature. The viscosity may be high due also to its intrinsic nature or because of precooling prior to spraying into the ccld leaching solvent.

Whether a spongy mass or strings or pellets is desirable or not depends upon conditions of the leaching operation. A spongy mass is desirable where conditions of the leaching are quiescent because leaching takes place more rapidly due to the thinner sections of the crystallized oil. Thus, when leaching in solvents of high volatility, it is preferable to maintain the solvent particularly in the lower part of the leaching column in a substantially quiescent state. This may be accomplished by imposing superatmospheric pres-- sure on the solvent during the leaching operation. Pressure may be ismposed by introduction of an extraneous gas which is insoluble in the leaching solvent or which will not liqueiy at the low temperatures existing in the leaching column. Thus, I may use air, carbon dioxide or other gases under pressure suiiicient to suppress substantial boiling of the leaching solvent. I may also suppress substantial boiling at the lower part of the leaching column by controlling the escape of vaporized leaching solvent, such vaporization occurring when the relatively warm waxy oil contacts the cold leaching solvent. Thus, by controlling the operation of a valve positioned on top of the leaching column so as to maintain pressure on the liquid, I may suppress substantial boiling points below the upper portion of the column. A small amount of boiling at the top of the column is not detrimental to the success of operation of the process particularly when the rate of oil introduction is controlled fairly low so as to prevent agglomeration of crystallized waxy oil.

substantial amountfof oil has been leached out of the crystallized structure, otherwise the wax crystals will breakupintonely dispersed particles which are diicult toseparatefrom the oil solvent i solution by settling andthe like. i

` slow agitation is` desirablefunder` these conditions for the reason that the crystallized strings or pellets settle rapidlyto the bottom of the leaching column and `therefore must necessarily be agitated for thepurpose of permitting the leaching solvent to dissolve theoil. However, the agitation must not be so severe that the crystallized masses will break up into iinely dispersed waxv crystals. 'I'his precaution is particularly neces- A sary, as stated above; during the last stages of the i H,vent is one which has a goodisolvent power for leaching operation since `the leached particles comprise fragile. wax crystals `substantially in the shape o-riginally ycrystallized in the solvent but from which the `occluded oil has been leached out.

' Such crystalsbreakreadilywith substantial agitation into finely dispersed particles whereas when in an unbroken' state, the crystals settle readily Vto the bottom of the decanter. The agitation may be accomplished byl providing a stirring device inthe leaching column as is Well known to those 's killed'in the art. The stirrer is preferablyoperated veryslowly, merely sufficient to churn the crystallized masses. In a countercurrent leaching process where the oil is introduced into the topof a leaching column and solvent at the bottom, the agitation accompanying the introduction of solvent at the bottom of the leaching column may be surlcient to preventthe strings or pellets of" crystallized oil from forming large masses to preventthe leaching solvent from producing-the desired results.v n

In general, the characterrof the' leaching soloil but not for the wax at low temperatures. As

leaching solvents, I may employ any of the liquefled normally gaseous hydrocarbons, such as ethane, propane, butane, iso-butane, or mix-tures thereof. I may -alsoemploy such normally liquid hydrocarbon solvents as pentane, hexane, etc.,`cas inghead gasoline, naphtha, etc. At low temperatures, the hydrocarbon solvents readily dissolve the oil from the crystallized Wax oil but dissolve substantially none of the wax; Other solvents which may be employed comprise alcohol, ether, mixtures of alcohol and ether, acetone, benzol or mixtures of acetone and benzol, and chlorinated normally gaseous hydrocarbons' such asI methylene chloride and dichlcrethylene.

` When employing lidueedfnormally gaseous hydrocarbons, `the temperature of the leaching solvent is preferably reduced by `vaporizing` a portion ofthe solvent under reducedpressure to substantially the boiling'point of the solvent.' `Normally liquid solvents may be chilled by circulating them. in indirect'heat exchange with a refrigerating medium, such as cold brine or by commingling the normally liquid solvent with a liquefied norrnallyfgaseous hydrocarbon such asliquid propane and effect the `chilling by vaporizing the normally gaseous hydrocarbon under reduced pressure. To

' effect the chilling of the normally liquid solvent,

other .liqueed normally gaseous materials may beV employed: such asl ammonia, liquid sulphur dioxide, methyl chloride, carbon dioxide and the like which `exert a refrigerated eiect by reducing the pressure and vaporizing the lidueed normally gaseous material.

Another feature of my invention resides in premixingl the waxy oil `with wax anti-solvents prior to introduction into the leaching solvent. Thus,

I may `commingle the waxy oil either at, below or `above the pour point of the waxy oil and subse-v quently spray or otherwise introduce the mixture' into the leaching solvent. If desired, I may mix the waxy oil with the wax anti-solvent at a temperature above the pour point of the oil, then precool the mixture to obtain good crystallization of the wax in the mixture and subsequently introduce the chilled mixture into the leaching solvent. I may rst obtain the desired crystallization of the wax in the oil and subsequently dilute the chilled oil with a wax anti-solvent and then leach `out the occluded oil. As wax anti-solvents I may employ naphtha preferably having a boiling range between 200 and 300 F., alcohols such as methyl, ethyl, propyl or butyl or mixtures thereof, chlorinated lighthydrocarbons such as dichlorethylene and trichlorethylene, mixtures of benzol and the like and aceto-ne or other ketones,

.mixtures kof benzol and the like and butanol or `be desirable' to useacetone, perhaps with small amounts ,of benzol of toluol, for the predilution and obtaining good crystallization of wax prior to leaching and subsequently eiiect the leaching in benzol or toluol. l

It is thus an object of my invention to accomplish dewaxing of waxy oils by spraying the waxy oil'into a cold leaching solvent so as toobtain 'solidication of the waxy oil and subsequently leach out the occluded oil from the solidified masses to leave a substantially oil-free wax. It is an obj-ect of the invention to control the size of the oil stream introduced into the cold leaching solvent so as to obtain crystallized oil particles which may be readily leached by means of the leaching solvent.

f An important object of the invention is to employ as leaching solvents, such materials which have a good solvent `power for oil but not for wax at low temperaturesi It is a particular object of the invention to ernploy `a liqueed normally gaseous hydrocarbon such as propane as the leaching solvent and to prevent ebullition in the lower portion of the leaching column so as 'to-prevent breaking oi the wax matrices intoinely dispersed particles. In other words, it is an object of the invention to produce suiciently large wax crystals or particles which may be readily removed from the oil solvent solution by settling.

It is another object of the invention to accomplish good crystallization of wax in the oil and subsequently leach the occluded oil from the wax by means of a solvent to leave a matrix substantially free from oil lwhich may be readily separated from the oil solvent solution byv settling.

- Another object'of the invention resides` in'c'ommingling the waxy oil with a wax anti-solvent and subsequently leach out the oil by'a cold solvent adapted to dissolve the oil but not the wax at a low temperature.

Another object of the invention resides in commingling the waxy oil with a good wax antisolvent and obtain good crystallization of the wax in the presence of a wax anti-solvent prior to leaching and subsequently leach outv the oil from the mixture in the presence of a solvent which has a good solubility for the oil but not the wax.

Other objects and features ofmy invention will be apparent from the following description of the drawing which is not to be considered as limiting.

Referring to the drawing, the waxy oil in tank I at a temperature above its congealing `point is withdrawn through line 2 controlled by valve 3 and pumped by pump 4 through line 5 and valve 6 through spray head 'I where it is passed countercurrent to a leaching solvent at a low temperature as will be further described.

Instead of spraying the waxy oil directly into the leaching column, I may rst subject the waxy oil to a prechilling operation by closing valve 6 and opening valve 9 on line IIl and passing the waxy oil into mixer or chiller II which is provided with a propeller agitator and scraper I2 operated by pulley I4 connected to a suitable source of power not shown. Chamber I I may be operated either as a mixing chamber or as a chilling chamber or both. Chilling in chamber Il may be accomplished by expanding a refrigerating material through jacket I5 such as liqueecl normally gaseous hydrocarbon as liquid propane withdrawn from storage tank AI6 via line I'I controlled by valve I1 and pump I9 which forces the liquid propane through line 20 and pressure reduction valve 20' into jacket I5. The vaporzed propane leaves jacket I5 via line 22 and valve 22 and passes into line 23. The temperature in jacket I5 may be controlled by operation of valve 22 which controls the pressure in the jacket. into line 23 from all apparatus in which propane is vaporized is recovered by compressing in compressor 24 where the pressure on the propane gases is increased and then passes via line 25 to condenser 26 where the compressed propane is liqueed which then iiows through 2'I into propane storage tank I6. Instead of expanding liquid propane into jacket I5 to eiect the desired refrigeration, I may expand other liquid materials which are normally gaseous under ordinary temperatures and pressures and which accomplish a refrigeration when expanded. Such materials may comprise liquid ammonia, liquid sulphur dioxide, liquid carbon dioxide, methyl chloride and the like. If desired, I may circulate a cold liquid through the jacket to eiTect the desired refrigeration. This may comprise the dewaxed cold solvent oil solution prior to removal of the solvent from the oil. If desired, a small amount of the liquefied normally gaseous hydrocarbon may be mixed with the waxy oil and chilling accomplished by vaporizing the solvent under reduced pressure.

The extent of refrigeration of the waxy oil will depend upon the particular conditions under which the operation is desired to be carried out. For example, I may merely chill the waxy oil to slightly above its pour point, say 120 F. for an oil having a viscosity of 240 seconds Saybolt Universal at F. and then spray the waxy oil into the leaching solvent, or I may chill to below The vaporized propane passingl the'p'our point of the oil as for example, 60 F. prior to the leaching operation. In connection with the latter operation, the waxy oil may be subjected to suiiiciently low temperatures to accomplish crystallization of the wax in oil prior to leaching. One desirable method of operation is to eiect the precrystallization of wax gradually by chilling to, say the pour point of the oil, F. for example, and obtaining some crystallization of the wax, the oil being substantially in the form of a gel. This gel may be broken by slowly agitating the gel such as by means of agitator I2 to obtain a uid mass. The partially chilled mass may then be further chilled to a lower temperature than the pour point of the oil, say 40 F. to obtain further crystallization of the wax and gelling of the oil which may again be broken by agitator I2. After substantially all of the wax has been crystallized and the gel broken in such manner as to not obtain substantial disruption of the wax crystals, the mass may be introduced into leaching column 8 via line 28 controlled by valve 28' and pump 29 which forces the chilled mass through spray l.

If desired, the waxy oil may be gradually chilled without substantial agitation to low temperatures, for example 0 F. to crystallize substantially all of the wax from the oil and allowed to digest at this temperature for a period of time until good crystallization of the wax has resulted. Then it may be comrningled with a diluent introduced into mixer II vialine 30 controlled by valve 30 so as to obtain a fluid porridge-like mass which may be readily pumped through the spray head 1. The admixture of diluent as, for example, naphtha, may be effected by means of agitator I2. However, this admixture is preferably under slow agitation so as not to break the wax crystals.

In leaching column 8, the sprayed oil upon contact with the cold leaching solvent at the top of the leaching column, is immediately solidied and in passing countercurrent to leaching solvent introduced at the bottom of the column, the solidified oil is dissolved in the leaching solvent, leaving a wax matrix at the bottom of the leaching column substantially free from oil.

Where a normally gaseous liquefied hydrocarbon, such as liquid propane, is employed as the leaching solvent in column 8,. the liquid propane is Withdrawn from propane storage tank I6 via line II controlled by valve I'I to pump I9 which forces the propane through line 3| controlled by valve 3| into propane chiller 32 where a portion of the liquid propane is vaporized by opening valve 33' on line 33. The vaporized propane being released through valve 33' passes through line 33 into line 23. By reducing the pressure in chiller 32 to substantially atmospheric, the temperature of the remaining propane will be lowered to substantially 40 F. The propane in chiller 32 at 40 F. is withdrawn via line 34 controlled by valve 34 and pumped by pump 35 into the bottom of the leaching column 8 via a perforated spider 36.

The amount of leaching solvent introduced into the column 8 will depend upon the character of the solvent and the character of the waxy oil. I have obtained good results when using a liquefied normally gaseous hydrocarbon, such as liquid propane, as the leaching solvent with as low as four volumes of the propane to one of the waxy oil. However, by employing larger amounts of propane, say up to ten volumes of the propane to one volume of the oil, the leaching of the oil 75;

from the `solidiiiedloil and `wax Vwill take place more readily. It is not economically desirableto employ more than ten volumes of` thepropa'ne due nto. thelarge capacity of leaching columns requiredl to effect ther leaching operation. y

When employing a liquefied normally Vgaseous hydrocarbon such `as, propane as the leaching solvent, a portion ofthe solvent will vaporize ima mediately upon contact withthe oil, creating a turbulent condition in the column. This is not desirable since `'the `leached` wax matrices are readily disrupted `by any substantial agitation forming finely dispersed wax particles which are difficult to separate from `the `oil solvent solution" 4by settling. llt is, therefore,preferableto main` tain quiescent leaching`'conditions and prevent `substantial boiling particularly at points i below' theV top of the leaching column. Substantial-boiL ing may be prevented by controlling the vaporisa-` tion of the solvent such as occurs when vthe relativelyfwarmfoil contactsthe leaching solvent. This vaporization `will" create a pressure in the column .which will suppress tendency `of the leaching 'solvent tov boil in the lower portion `ogf the-leaching column. The pressure may be controlled'by means ofvalve '51" on line 3l.l Vapors removed from the Vleaching column pass vialline 3l into line/3. If desired, the boiling in the leaching column may be substantially prevented by superimposing a gas in the leaching columnV 'which is substantially insoluble in the oil and This gas may be introduced via line i propane. 38 controlled by valve 38' and may comprise air, carbondicxide or other non-miscible gas. It is desirable to prevent infiltration of heat from the i outer walls"*o`f` the leaching` column since this causes the normallyliqueed gaseoushydrocar-k bon or `leaching solvent to boil in the column. One method `for preventing' this is to provide a jacket 35 around thecolumn and circulate aucold` medium through the jacket, the cold medium being at or `preferably.below-the temperature of the v'contentsfin the column. resides in taking propane under superatmospheric pressure fromstorage tank "I6 andnexpanding it into the jacket'via line I1, pump I9,-li`ne 40 and expansion valve 40'. The expanded gases leaving the jacket vialine 4l' are passed into line `23 via line 50. If desired,` I may expandethaneor a solvent having a lower boiling point than the the-temperature oi the leachingsolvent so asto provide la temperature in the jacektlower `than that existing in the column.` V

Theleached wax matrices accumulating at the bottom of the leaching column and which have been thoroughly` washed by means of fthe/.fresh propaneintroducedvia' line 34 and spider 36 are withdrawn -from the column by means of gear pump 45. The removal of the wax matrices from the column is aided" by paddle "42 on shaft 43 which is rotated by pulley 44 connected to a suit` able source of power not shown. The paddle-"42 is turned very slowly, merely sufiicient to gently agitatethe wax slurry accumulating at the bottom of the column and to passthe wax slurry to gear pumpf`45, VGrear pump 45 `forces the waxthrough line 46 controlled by valve 46 into 'evap` oratorftl where the small amount of propane o`c`'` cluded in` the wax is vaporized by.l thet aid of 3 The ivaporiaedpropane (passing through mist` ex-` tractor ilis withdrawnfrom the column via line steam circulated through closedl coil 48.

5t controlled by valve 5G and passed into line 23. The wax" at theV bottom of thevaporator` substantially free from entrainedpropane is Witha separate, evaporator.

Another method i drawn sent by means of pump 54 through line 55 into via une 52 controlled by valve 52' and@ ywax storage 'tank"55.. The solution of oil and `propanecarrying a small amount of entrained i crystalline wax which had not settled to the bottom of thelleaching column is Withdrawn via line 5l` controlled by valve 51 and pumped by pump 59 viaf line. to through lter @I where the en- 1trained precipitated wax is separated andremoved via line 62 controlled by valvel G2' and pump 64 which introduces the Wax into 1inev46 `and evaporator All where the propane is vaporized.

Ii desired, this wax may be recovered separately in which case the wax slurry Will be passed into The clear solution is thenv passed through line 65 through heat exchanger t6 where the tem-` perature of the clear solution is raised, after which the preheated solution passes via line 61 into evaporator t3. If desired, the cold propane oil solution may be circulated through jacket i5 of mixer il to effect the cooling of the incoming oil and then passed into evaporator 68. The propane in evaporator 5S is vaporized, aided` by steam circulating through closed coil $9. rIuhe vaporized propane passing through` mist extractor 10 is ywithdrawn via line 'il controlled by valve l l and-sent into line 25. The wax free oilis withf drawn from the bottom of the evaporator via line v'i3 controlled by valve 14 and pumped by pump 15 into devvaxed oil storagetanl; i6;

l As stated above, theuvaporized propane collecting fromV all apparatus in line.23 is sent to compressor 24 where the pressure on the propane gases is raised, after which it is liquefied in condenser 25 and `retlirned to propane storage Theforegoing Vdescription of the drawing'has been made with reference to carrying out a process of dewaxing without aid of wax` anti-solvents. Wax anti-solvents, such `as liquid sulphur dioxide, ora mixture or acetone and benzol or toluol or any of the Wax anti-solvents herein mentioned,

may be used to aid conditioning the waxy oil prior to the leaching operation. Such wax anti-solvents `may be mixed with the waxy oil in a mixing tank U and-are withdrawn from storage tank "i1 via line 78 controlled by valve lf3 and pumped by pump 3i] through line 8i into the mixer l I. If de-Y sired, the wax anti-solvents may be mixed directly with the oil at a temperature above the pour point and then sprayed into vthe leaching column, or' i aiteradmixture with the waxy oil, the mixture may` becooled by any of the methods herein described toa temperature at or below the pour` point,v of the oil so as to obtain good crystalliza-` tion of the wax prior to the leaching operation. The chilling may be accomplished in such manner as stated above, thatv is,chilling the oil to form a gel and woriringA this gel to break it up andform a fluid mass which may then be pumped into the leaching column. Preferably, however,

the vvaxy oil is chilled to obtain the crystallization ofthe wax-and subsequently commingled with the wax antiLsolvent or the waxy oilmay be rst Thismay be accomplished by condensing the vaporized diluent'and wax anti-solvent in evaporators 41 and 68 to obtain condensation of the wax anti-solvent if such has a higher boiling point than the diluent or condensation of the diluent if the boiling point of the diluent is higher than that of the wax anti-solvent and then collecting the condensate as a separate fraction. The unvaporized material may then be liqueiied by compression and cooling if this material comprises a liquefied normally gaseous hydrocarbon diluent.

The following represent examples of the op- .eration of the portion forming the subject matter of my invention:

l Example 1 A rainate produced by extracting a waxy distillate with a mixture of liquid sulphur dioxide and benzol and having an A. P. I.v gravity of 31.5, a viscosity of 50 seconds Saybolt Universal at 210 F., a pour point of 120 F. and a Wax'content of approximately 25% was sprayed into the cold propane at a temperature of about 125 F. which is slightly above the pour point of the waxy oil. Propane was introduced into the bottom of the leaching column countercurrent to the waxy oil and was at a temperature of 40 F. The amount of propane introduced into the leaching column was in the ratio of about 7 volumes of propane for every volume of waxy oil sprayed into the column. After washing the wax countercurrently in; the leaching column and ltering the oil solvent solution decanted at the top of the column to remove a small quantity of suspended wax, the solvent wasv distilled from the oil, the recovered oil had a pour point of F., and A. P. I. gravity of 29, a viscosity of 53 seconds Saybolt Universal at 210 F. and was recovered in a yield of 72%. The wax after vaporizing the propane had a melting point of 130 F. and was recovered in a yield of 27%.

Example 2 A raw distillate from a Santa Fe Springs crude having an A. P. I. gravity'of 20 and a viscosity of 70 seconds Saybolt Universal at 210 F. and a pour point of 115 F. was chilled to a temperature of 40 F. in a device such as mixer Il and mechanically agitated to break up the wax gel structure giving a porridge-like mass which was then sprayed into cold propane at *40 F. Propane at a temperature of 40 F. in a ratioof about volumes to one of the waxy oil was introduced into the bottom of the leaching column in the manner heretofore described. A yield of oil equal to 80% of the original was recovered having a viscosity of 74 seconds Saybolt Universal at 210 F. and a pour point of 0 F. The recovered wax had a melting point of 128 F. and was obtained in approximately 20% yield.

Example 3 'I'he same structure as in Example 2 was mixed with an equal volume of a mixture of 50% acetone and 50% toluol and the mixture cooled to F. with slow agitation. This mixture was then passed into cold propane and extracted with 5 volumes of propane at a temperature of 15 F. to one volume of the waxy oil. The recovered oil had a pour point of 5 F., a viscosity of 72 seconds Saybolt Universal at 210 F. and was recovered in a yield of 81%. The wax had a melting point of about 129 F. and was recovered in a yield of about 19%. y

The foregoing exemplary description of my invention is not to be considered as limiting since many Variations may be made within the scopeV of the following claims by those "skilled`in the art without departing from the spirit '.thereof.

I claim:

, 1. A process for dewaxing oils which comprises spraying waxy oil into al cold liqueednormally gaseous hydrocarbon solvent capable of dissolving oil at low temperatures but not substantial quantities of wax, solidifying said sprayed oil by means of said cold solvent to form a plurality of frozen particles of wax and oil, extracting the occluded oil from said frozen particles by means of said cold solvent to leave wax matrices substantially free from occluded oil without dissolving substantial amounts of wax, said extraction being accomplished under superatmospheric pressure sucient to prevent substantial ebullition of solvent during the extraction of oil from the solidiiied waxy oil particles, removing the oil solvent solution from the wax matrices and separating the solvent from the oil.

2. A process as in claim 1 in which the cold solvent comprises liquid propane.

3. A process for dewaxing oil which comprises spraying a waxy oil into a leaching column containing a cold liquefied normally gaseous hydrocarbon solvent capable of dissolving oil at low temperatures but not substantial quantities of wax and maintained under controlled superatmospheric pressure sulicient to prevent substanltial ebullition of solvent upon contact with the waxy oil and to prevent substantial agitation of the wax matrix after substantial quantities of oil have been extracted from the waxy oil by means of said solvent, freezing and solidifying said waxy oilby means oi said cold solvent, allowing said frozen oil .to contact said cold solvent for suicient time to permit said solvent to extract occluded oil in said frozen waxy oil and to leave a solidied wax matrix substantially free from occluded oil, separating the oil dissolved in said solvent from the wax matrix and separating the solvent from the oil.

4. A process as in claim 3 in which the vaporization of solvent caused by contact of the waxy oil with the solvent is controlled so as to maintain a superatmospheric pressure in the leaching column.

5. A process for dewaxing oils which comprises spraying a waxy oil into the top of a leaching column containing a cold liqueed normally gaseous hydrocarbon solvent capable of dissolving oil at low temperatures but not substantial quantities of wax, introducing cold leaching solvent intolthe bottom of said leaching column, freezing and solidifying said waxy oil by means of said cold solvent, allowing said frozen oil to contact said cold solvent for a sufficient length of time to permit said solvent to leach out occluded oil in said frozen waxy oil and leave a solidified wax matrix substantially free from occluded oil at a lower portion of said leaching column, preventing substantial agitation of said wax matrix in the lower portion of said leaching column, by controlling vaporization of solvent from said leaching column so as to maintain a superatmospheric pressure in said leaching column, removing the wax matrix from the lower portion of the said leaching column and the solution of oil and solvent from the top of said leaching column, filtering said oil solvent solution to remove the entrained wax particles and separatcrystallized wax, oil and solvent liquid in a vessel, displacing oil and solvent liquid from said mass in said Vessel by introducing a solvent liquid into one end o f said Vessel whilewithdrawing oil and solvent liquid from the other end `of saidv vessel, said displacement being carried out Withf 

